Wrist-worn ECG monitor

Abstract

A compact, lightweight wrist-worn cardiac data and event monitor having dry skin electrodes integral with the monitor's housing is disclosed. Preferably, the skin electrodes are made of titanium nitride-plated stainless steel and form inner, wrist-contacting, and outer, other hand's palm-contactable regions of the housing. Chronometric and other multiple functions are provided to increase the functional density of the monitor by partitioning and very-large-scale-integrating the circuitry, which includes signal detection; data conversion, storage, display and telecommunication; and external pushbutton controls operable by the patient's other hand. In accordance with the preferred embodiment, a telephonic transmitter is integrally included within the housing for remote diagnostic purposes without the need for external connections. By a preferred method of the invention, a simplified digital filter implemented in firmware ensures that only ECG and event data are recorded at the exclusion of noise and motion artifacts. By another preferred method of the invention, a battery life prediction method is used to extend the useful life of the battery and to indicate to the patient when the battery should be replaced. Event data that may be recorded and tele-transmitted along with the ECG data include time-of-day or elapsed time markers, as well as markers or indications of the detection of any pulses produced, for example, by an implanted pacemaker or an implanted cardio-verter/defibrillator monitor (ICDM).

It is claimed and desired to secure by Letters Patent: 
     
       1. A wrist-worn monitor comprising: a housing suitable for attachment to a user's wrist;   plural electrodes integral with said housing for contacting a patient's skin;   signal detecting means integral with said housing and operatively connected with said electrodes for detecting cardiac activity represented by variations in the resistance of the patient's skin and for producing an ECG signal;   an analog-to-digital signal converter integral with said housing and operatively connected with said signal detecting means and responsive to said ECG signal for producing ECG data;   event detecting means integral with said housing and coupled with said converter for determining that a cardiac event has occurred, said event detecting means producing a trigger signal;   recording means integral with said housing and coupled with said converter and said event detecting means and responsive to said trigger signal for recording selected EDG data proximate in time to such cardiac event; and   transmitting means coupled with said recording means and integral with said housing for wirelessly communicating said recorder ECG data by producing a modulated ECG data carrier for telephonic transmission to a remote site.   
     
     
       2. The monitor of claim 1, wherein said electrodes are formed of a base metal a region of which is plated with a composition of titanium and at least one other element chosen from the group consisting of nitrogen and carbon. 
     
     
       3. The monitor of claim 2, wherein said composition is titanium nitride. 
     
     
       4. The monitor of claim 2, wherein said composition is titanium carbide. 
     
     
       5. The monitor of claim 2, wherein said composition is titanium carbo-nitride. 
     
     
       6. The monitor of claim 1 which further comprises implant detecting means integral with said housing and coupled with said converter and said recording means for detecting a pulse produced by an implanted pacemaker or defibrillator and for recording with an associated ECG data record an indicium of the occurrence of such pulse. 
     
     
       7. The monitor of claim 1 wherein said transmitting means includes a speaker for producing audible trans-telephonic communication of said recorded ECG data. 
     
     
       8. The monitor of claim 1 further comprising digital filtration means integral with said housing and coupled with said converter, said event detecting means and said recording means, wherein said digital filtration means performs the steps comprising: sampling said ECG data to produce a set of successive ECG data samples;   a first calculating step whereby a first filter output value equal to a first weighted average of plural ones of said successive ECG data samples is calculated, wherein the contributions of said ones to said weighted average are related to one another by powers of two;   a second calculating step whereby a second filter output value equal to a second weighted average of at least one previous of said first filter output values and at least one previous of said second filter output values is calculated, wherein the contributions of said output values to said second weighted average are related to one another by powers of two; and   repeating said first and said second calculating steps to produce digitally filtered output ECG data for further processing by said event detecting means and said recording means as a candidate QRS complex.   
     
     
       9. The monitor of claim 1 further comprising: a battery integral with said housing and coupled with said converter, said event detecting means and said recording means; and   battery end-of-life predicting means integral with said housing and coupled with said battery;   wherein said battery end-of-life predicting means performs the steps comprising: predetermining a power capacity value for said battery; and repeatedly thereafter measuring the current drain on said battery while said monitor is being supplied with power therefrom,   calculating the power being consumed by said monitor based upon said measuring, and   comparing the result of said calculating with said power capacity value; then     based upon said comparing, determining whether said consumed power is approximately equal to said power capacity value; and if so then   annunciating on said monitor the impending end-of-life of said battery.     
     
     
       10. An ECG data monitor comprising: a unitary housing;   plural electrodes integral with said housing for contacting a patient's skin;   signal detecting means integral with said housing and operatively connected with said electrodes for detecting cardiac activity represented by variations in the resistance of the patient's skin and for producing an ECG signal;   an analog-to-digital signal converter integral with said housing and operatively connected with said signal detecting means an responsive to said ECG signal for producing ECG data;   recording means integral with said housing and coupled with said converter for recording ECG data; and   transmitting means coupled with said recording means and integral with said housing for wirelessly communicating said recorded ECG data by producing a modulated ECG data carrier for telephonic transmission to a remote site.